Conventionally, there has been proposed a variety of containers for microwave oven. For example, see Japanese patent publication No. 2008-290738 (A).
Japanese patent publication No. 2008-290738 (A) discloses a cooking container for microwave oven of which a peripheral sealing portion is formed over a whole circumference of a flanged portion of a container body formed of synthetic resin, and a lid material is thermally fused to the peripheral sealing portion. The peripheral sealing portion is provided with a V- or U-shaped projection extending interiorly of the container (i.e., an opening side). In accordance with this conventional cooking container for microwave oven, moisture of the content is heated up in the microwave oven and the inner pressure in the microwave is thus increased. As a result, the lid material is pushed up, and a part of the lid material is automatically removed or separated from the inward projection. For the above reason, a user do not need open the lid material before putting the container in the microwave oven.
On the other hand, this cooking container for microwave oven is provided with an annular portion formed along the inner periphery of the opening of the container in the peripheral sealing portion except for a projection for vapor discharge. The flanged portion is provided with a clearance which is present in a range from the annular portion to the opening, and in which the flanged portion and the lid material are not thermally fused. The content may enter the clearance. In view of the point that the content may compromise the looking or appearance of the flanged portion, the less or narrower clearance is desired. For this reason, the annular portion is preferably located adjacent to the opening of the container.
However, in the cooking container for microwave oven as described in Japanese patent publication No. 2008-290738 (A) the projection for vapor discharge projects or extends from the annular portion toward the opening side in the peripheral sealing portion. Due to this the annular portion is necessarily located away from the opening of the container body in an amount corresponding to a projecting amount of the projection. Accordingly, the annular portion is hardly disposed adjacent to the opening of the container, thereby needing to take measures.